1. Field of the Invention
The present invention relates to an optical pick-up actuator.
2. Description of the Related Art
In general, an optical pick-up actuator is an apparatus that uniformly maintains the position of an objective lens with respect to an optical recording medium, such as a CD or DVD, by driving a lens holder containing the objective lens in focusing, tracking, and tilting directions, in order to follow the tracks in the optical writing medium.
FIG. 1 is a perspective view of an optical pick-up actuator according to the related art.
Referring to FIG. 1, an optical pick-up actuator according to the related art includes a lens holder 2 having an objective lens 1 installed therein. A focusing coil 3 and a tracking coil 4 are respectively wrapped around the lens holder 2.
Four wire springs 5 are fixed on the lens holder 2. The wire springs 5 electrically connect the focusing and tracking coils 3 and 4.
The lens holder 2 is supported by magnets 6 provided on a base 7 of the actuator. The magnets 6 are fixedly installed on a yoke 8 to face the focusing and tracking coils 3 and 4. The yoke 8 may be integrally formed with the base 7, or separately attached to the base 7.
A wire holder 9 for fixing the opposite ends of the wire springs 5 is formed at one side of the base. A circuit board 10 is installed on the rear surface of the wire holder 9.
FIG. 2 is a perspective view showing wire springs coupled to a lens holder in an optical pick-up actuator according to the related art.
Referring to FIG. 2, a fixing protrusion 11 is formed on either side at the top and bottom of the lens holder 2. The fixing protrusion 11 has a through-hole 12 through which the wire spring 5 passes.
A connecting protrusion 13 is formed facing each of the fixing protrusions 11 on either side surface of the lens holder 2. A stepped receiving portion 11a is formed on the outer surface of the fixing protrusion 11. The wire springs 5 electrically connect the focusing coil 3 to the tracking coil 4 at the connecting protrusion 13.
In order to couple the wire springs 5 to the lens holder 2, the wire springs 5 pass through the through-holes 12, and an adhesive epoxy is applied to the receiving portion 11a to adhere the wire springs 5 to the lens holder 2.
However, the receiving portion 11a is only stepped, and there is no structure provided to prevent the applied epoxy from flowing to the adjacent structures. Thus, during the process of applying adhesive, the adhesive may drip from the receiving portion 11a and the fixing protrusion 11, causing a loose attachment between the wire spring 5 and the lens holder 2.
Also, in the process of applying adhesive to the outer surface of the fixing protrusion 11, if the adhesive should drip elsewhere, more adhesive needs to be used in lieu of the dripped adhesive, thereby wasting adhesive.
Additionally, when an excessive amount of adhesive is applied, the weight of the lens holder 2 increases, thereby deteriorating the driving characteristics (such as focusing and tracking) of the lens holder, which focuses light onto a disk.
FIG. 3 is a sectional view taken along line III-III of FIG. 1.
Referring to FIG. 3, the wire holder 9 is either coupled to the base 7 or integrally formed with the base 7. There are four filling holes 14 formed in the wire holder 9. The filling holes 14 extend a predetermined depth into the wire holder 9 from its front surface. The filling holes 14 may alternately be opened at the front and the sides.
Through-holes 15 having almost the same diameter as the wire springs 5 are formed through the wire holder 9, so that the opposite ends of the wires 5 are inserted through the filling holes 14 and the through-holes 15, reaching the rear surface of the wire holder 9.
A damper material 16 made of an ultraviolet ray hardenable viscoelastic material that has undergone gelation is filled to enclose the wire spring 5 inside the filling hole 14. Here, the liquid damper material 16 that is injected into the filling hole 14 is formed using ultraviolet ray exposure for quick hardening, resulting in a viscoelastic material.
Also, the other ends of the wire springs 5 are soldered to a land of the circuit board 10 at the rear surface of the wire holder 9, to induce the flow of current through the focusing and tracking coils 3 and 4.
During operation, the magnets 6 emit magnetic fluxes transversely to the direction of current flowing through the focusing and tracking coils 3 and 4.
A vertical force is generated from the current flowing through the focusing coil 3, so that the lens holder 2 moves the objective lens 1 in a focusing direction.
Likewise, a horizontal force is generated from the current flowing through the tracking coil 4, so that the lens holder 2 moves the objective lens 1 in a tracking direction.
Here, due to the movement of the driving portion formed of the objective lens 1 and the lens holder 2, the wire springs impart elasticity on the lens holder 2, so that the driving portion generates fine vibrations.
The vibration distortions thus generated are absorbed by the viscoelastic material 16, so that the vibrations from the driving portion are reduced or eliminated.
However, the assembly process of radiating ultraviolet rays onto the damper material 16 to obtain a predetermined viscoelasticity thereof, following the filling of the liquid damper material 16 in the filling hole 14, requires much equipment and manpower. In addition, the assembly process suffers from the problems of having to quickly inject the filling hole 14 with damper material 16, and non-uniformity in performance of the damper material 16.
For example, because damper material 16 for filling into four separate filling holes 14 in the wire holder 9 is contained in a single syringe (which must fill the holes one by one), the quantity of damper material 16 filling each of the filling holes 14 may be excessive or insufficient, and bubbles may be formed inside the filling holes 14, so that the hardness may vary, causing the damping characteristics of the damper material 16 in each hole to be non-uniform.